Zoned roof monitoring system

ABSTRACT

A leak in the membrane of a generally horizontal roof support deck includes dividing the membrane into separate zones and locating a sensor to detect moisture underneath the membrane. A unique digital code address is assigned to sensor where inputs of the sensors are connected to a single power and signaling cable system using a daisy chain. The serial bus controller is to interrogate each of the sensor devices using the address to identify zones where moisture is detected. A transmitting antenna is provided at each sensor which is switched on when moisture is detected for detecting of the sensor from above the membrane by a utility locate device to confirm the location of the sensor.

The present invention relates to a system for monitoring moistureintrusion in roofing and waterproofing systems for the presence andlocation of moisture penetration. It has particular application tomonitoring low-slope and flat roofs of residential and commercialbuildings for undesired water ingress.

BACKGROUND OF THE INVENTION

The failure to detect, identify and correct minor roof deterioration andleakage in the earliest stages is considered the greatest cause ofpremature roof failure. This is particularly true of roofing materialsapplied on low-slope or flat roofs. Costly roofing problems are oftenthe result of design deficiencies, faulty application, or trade damageof the roof system. Even when properly designed and applied, all roofingmaterials deteriorate from exposure to the weather at rates determinedlargely by the kind of material and the conditions of exposure.Conventional roof designs in cool climates often have water accumulationbelow the membrane caused by vapor drive from below.

It is known to provide a moisture sensing system arranged in separatezones of the roof where the moisture sensing system of each zone must bewired back to a central monitoring station for individual monitoring.The wiring requirements for such a system are very onerous and prone todamage.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a method formonitoring leaks in flat or low slope roofing and waterproofing systemswhich have an impermeable membrane applied at the top most layer of theassembly where the complexity of wiring requirements is reduced.

In a first aspect of the invention, all the sensing systems areconnected to a single power and signaling cable using a daisy chainmethod. The cable contains a pair for the serial bus, a pair forpowering and a pair for a locate tone signal.

According to a first definition of this invention there is provided amethod of detecting a leak in a roof, wherein the roof comprises agenerally horizontal roof support deck with a water impermeable membraneapplied on top of the roof assembly, the method comprising:

dividing the membrane into a plurality of separate zones;

in each zone applying at or adjacent the membrane a sensor devicearranged to detect moisture underneath the membrane;

the sensor device in each zone including remote measurement andsignaling electronics;

assigning a unique digital code address to each of the remotemeasurement and signaling electronics;

connecting inputs of the remote measurement and signaling electronics ofthe sensor devices to a single power and signaling cable system using adaisy chain;

terminating the signalling cable system in a serial bus controller;

and using the serial bus controller to interrogate each of the sensordevices using the address to identify zones where moisture is detected.

According to a second definition of this invention there is provided amethod of detecting a leak in a roof, wherein the roof comprises agenerally horizontal roof support deck with a water impermeable membraneapplied on top of the roof assembly, the method comprising:

dividing the membrane into a plurality of separate zones;

in each zone applying under the membrane a sensor device;

wherein the sensor device includes sensors arranged to detect moistureunderneath the membrane, humidity in a location surrounding the sensordevice and temperature in a location surrounding the sensor device.

the sensor device in each zone including remote measurement andsignaling electronics.

According to a third definition of this invention there is provided amethod of detecting a leak in a roof, wherein the roof comprises agenerally horizontal roof support deck with a water impermeable membraneapplied on top of the roof assembly, the method comprising:

dividing the membrane into a plurality of separate zones;

in each zone applying at or adjacent the membrane a sensor devicearranged to detect moisture underneath the membrane;

the sensor device in each zone including remote measurement andsignaling electronics;

wherein each sensor device includes an antenna for emitting a locationsignal and a switching device for activating the antenna.

where a locate tone signal, on command at the sensor device, the isswitched on at the sensor device to energize the antenna of the sensordevice;

and wherein, on detection of moisture by a sensor device, the locatetone is switched on to the respective antenna of the sensor device and atechnician locates from above the membrane the sensor device emittingthe tone signal using a locate receiver.

According to a fourth definition of this invention there is provided amethod of detecting a leak in a roof, wherein the roof comprises agenerally horizontal roof support deck with a water impermeable membraneapplied on top of the roof assembly, the method comprising:

dividing the membrane into a plurality of separate zones;

in each zone applying at or adjacent the membrane a sensor devicearranged to detect moisture underneath the membrane;

the sensor device in each zone including remote measurement andsignaling electronics;

assigning a unique digital code address to each of the remotemeasurement and signaling electronics;

connecting inputs of the remote measurement and signaling electronics ofthe sensor devices to a single power and signaling cable system using adaisy chain;

terminating the signalling cable system in a serial bus controller;

wherein the serial bus controller includes built in loop verificationtesting.

Preferably each sensor device also includes a sensor for humidity in alocation surrounding the sensor device and preferably each sensor devicealso includes a sensor for temperature in a location surrounding thesensor device. Sensors for detecting these parameters are commerciallyavailable and can be attached readily to the sensor device at therespective zone for communication therewith as required based on signalsfrom the sensor device to provide a reading when instructed.

In a preferred arrangement for use with external communication, theserial bus controller is driven by a microprocessor controller which isconnected to a remote server through an internet gateway.

Preferably the serial bus controller includes built in loop verificationtesting.

Preferably the signalling cable system contains a conductor pair for theserial bus for communication with the sensor devices and a conductor apair for powering the sensor devices.

In the preferred method, the sensor devices are interrogated from aremote monitoring station reading moisture levels in a locationsurrounding the sensor device and mapping the levels onto a chart foranalysis.

In an important feature, each sensor device includes an antenna foremitting a location signal and a switching device for activating theantenna. In this way a locate tone signal is provided and, on command atthe sensor device, the locate tone is switched on at the sensor deviceto energize the antenna of the sensor device. This allows the technicianto locate the sensor device at the membrane surface so as ensure thereare no location errors when a sensor device is triggered for furtheranalysis. That is, before an excavation of the roof membrane is orderedto determine the reason for a potential leak, the actual location of thetriggered sensor device is checked manually using a utility locatereceiver which responds to the signal from the antenna. It will beappreciated that signalling or wiring errors could mislocate the sensordevice so that it is not at the position on the roof membrane where itis expected or intended to be. In this case, the mislocation can befound and the actual zone concerned investigated by excavation.

Thus preferably the signalling cable system includes a dedicatedconductor pair for the locate tone signal to be communicated to all ofthe sensor devices. Thus, on detection of moisture by a sensor device,the locate tone can be switched on to the respective antenna of thesensor device and a technician locates from above the membrane thesensor device emitting the tone signal using a locate receiver. Suchreceivers are readily commercially available and include a wand which isresponsive to the frequency emitted by the antenna. The devices areoften used to locate utility lines and are associated with a transmitterto apply the signal to the utility line. In this case the signal isapplied centrally through the daisy chain to all of the sensor devices.

In one preferred embodiment which can be used with the arrangementsdescribed above or as described below, the moisture is sensed by eachsensor device by applying to the roof in a location underneath themembrane and on top of a roof deck at least one length of a moisturedetection sensor tape arranged to detect moisture in between the deckand the membrane. In this case, the moisture detection sensor tape cancomprise a substrate of a dielectric material carrying first and secondelongate, parallel, conductors secured to one surface of the substrateand moisture is sensed by a sensing system detecting changes inresistance between said first and second conductors of said at least onelength so as to detect moisture permeating into the respective zone inthe location between the membrane and the roof deck. Preferably thelength or lengths of the tape are arranged in a two-dimensional arraysuch as at right angles so as to span across the zone with the sensordevice itself at an intersection of the lengths at the center of thezone. That is the zones may be rectangular and each of the first andsecond lengths spans across the zone passing substantially through acenter of the zone, either diagonally or parallel to sides of the zone.The zones can then be arranged in an array of rows and columns. Themoisture sensor tapes of each zone are preferably electrically separatedfrom the lengths of each of the other zones so that each zone isindependent.

The arrangement described in detail herein includes the steps of:

Laying out the roof assembly in a zoned construction whereby a dedicatedmoisture detection, temperature and humidity sensor is placed on thevapor barrier within each zone to detect any moisture intrusion into thezone;

Locating remote measurement and signaling electronics (RMSE) at everylocation in the roof assembly where moisture detection sensors arelocated for monitoring a selected zone;

Assigning a unique digital code address to each of the remotemeasurement and signaling electronics installed in the zones;

Connecting the dedicated sensors to the inputs of the remote measurementand signaling electronics at each zone location;

Connecting all the RMSEs to a single power and signaling cable using adaisy chain method with built in loop verification testing. The cablecontains a pair for the serial bus, a pair for powering and a pair for alocate tone signal;

Terminating the start of the cable system in a serial bus controllerdriven by a microprocessor controller which is connected to a remoteserver through an internet gateway.

Accessing and interrogating the RMSE from a remote monitoring stationreading the moisture levels, temperature, and humidity levels andmapping them onto a chart for analysis;

Placing a 32 KHZ tone place on a designated cable pair and on commandfrom the monitoring station, the tone is switched on at the RMSE toenergize the locate coil incorporated in RMSE. A technician can thenlocate the mislocated unit using a utility locate receiver.

In a second aspect of the invention, the system incorporates a hand-heldscanning unit which generates a powering field which energizes a sensorsystem located in the roof or wall assembly. Once energized, the sensorand scan unit communicate using a UHF low power transceiver system. Oncommand, moisture, and optionally temperature and humidity readings, aretaken and transmitted to the scanning unit for display and storage.

According to a definition of this invention there is provided a methodof detecting a leak in a roof, wherein the roof comprises a generallyhorizontal roof support deck with a water impermeable membrane appliedon top of the roof assembly, the method comprising:

dividing the membrane into a plurality of separate zones;

in each zone applying at or adjacent the membrane a sensor devicearranged to detect moisture underneath the membrane;

providing a movable scanning device having a power supply antenna forsupplying power by an electromagnetic wave to the sensor device;

moving the scanning device to selected ones of the zones;

at each selected zone causing the power supply antenna to supply powerto the sensor device in the zone;

using the power supplied, causing the sensor device to emit signalsrelated to the moisture underneath the membrane as detected by thesensor device;

and detecting the signals at the mobile scanning device.

Thus preferably each sensor device is unpowered and unconnected to powersupply wires and the sensor devices provide a wireless moisturemeasuring system.

In the preferred arrangement, the antenna uses a low frequency resonantantenna system in the scanning unit and the sensor device to energize asensor measurement circuit to detect the moisture underneath themembrane. The low frequency energizing signal can be modulated tocommunicate and transmit data between the scanning and sensor unit. Whenenergized, the sensor device can communicate with the scanning unit viaUHF transceivers employed in both the scanning unit and sensor device.

On command from the scanning unit, the sensor device can take resistancereadings on a moisture detection tape and transmits the data to thescanning unit.

The sensor device typically transmits the data to the scanning unit fordisplay and storage for future analysis.

While the system can operate simply to monitor moisture penetration, insome cases each sensor device also includes a sensor for humidity in alocation surrounding the sensor device and/or a sensor for temperaturein a location surrounding the sensor device.

The scanning unit is manually portable to be moved from one zone toanother zone.

This arrangement provides the ability to monitor and read moisturehumidity and temperature (MHT) readings from sensors which are imbeddedin building structure to monitor the performance of the buildingenvelope and roof structure. A portable interrogation unit generates anelectromagnetic field which transmits energy to an antenna located nearthe MHT sensors which is then rectified and powers up the sensorelectronics to initiate the measurement sequence. As the MTH readingsare made the sensor circuit passes the information to a radio frequencydata transmitter and antenna which transmits the readings to theinterrogation unit. The MTH readings are the displayed on the viewerdisplay and stores the data in memory with a location number and timestamp for further analysis.

The membrane may be loose laid, mechanically attached or fully adhered.

Thus the arrangement described in detail herein provides a leakdetection system by applied a pair of electrically conductive sensingelements on the surface of the vapor barrier or roof deck in anindividually zoned cross grid zone detection pattern so as to be inelectrical communication with any moisture that reaches the lower roofassembly.

The measurement system, on remote command, takes readings from the zonesand forwards the readings preferably via an internet gateway to acloud-based monitoring center for analysis. The individual grid sectionsare measured time stamped and logged with the resultant readings mappedonto an as-built drawing of the roof assembly. A color-coded map can beoverlaid on the drawing of the building to provide an intuitive overviewof the roof condition. If a leak occurs, stored measurements can be usedto determine the location of the first zone that went into alarm.

According to a further definition of the invention there is provided anapparatus for detecting a leak in a roof, wherein the roof comprises agenerally horizontal roof support deck with a water impermeable membraneapplied on top of the roof assembly, the apparatus comprising:

a sensor device arranged to detect moisture underneath the membrane;

the sensor device comprising a moisture sensing component responsive topresence of moisture to generate a change in signal indicative of thepresence of the moisture;

the sensor device comprising a control component arranged to receive thesignal and for generating a communication signal for transmission to aremote location;

the sensor device including an antenna operable to transmit a locationsignal to a receiver positioned above the membrane.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described in conjunction withthe accompanying drawings in which:

FIG. 1 is an exploded schematic cross-sectional view of a typicalconventional roof assembly

FIG. 2 is an illustration in plan of an X and Y sensor zone usingdetection tape with two flat conductors joined at the intersection ofthe tapes

FIG. 3 is a schematic plan view showing multiple zones for connection toa central monitoring unit.

FIG. 4 is a circuit schematic showing one embodiment according to thepresent invention of an arrangement for monitoring all of the zones.

FIG. 5 is a circuit schematic showing one embodiment according to thepresent invention of the sensing device used in each zone.

FIG. 6 is a schematic illustration showing another embodiment accordingto the present invention of an arrangement for monitoring all of thezones and showing the roof structure of FIG. 1 using a manually portablescanning device.

FIG. 7 is a circuit schematic showing a powering transmitter supplycircuit of the scanning device of FIG. 6 .

FIG. 8 is a circuit schematic showing the transceiver circuit of thescanning device and the sensing device of FIG. 6 .

FIG. 9 is a circuit schematic showing the measuring circuit of thesensing device of FIG. 6 .

FIG. 10 is a circuit schematic showing the powering circuit of thesensing device of FIG. 6 .

FIG. 11 shows the transceiver for the scanning unit of FIG. 6 includinga display and keyboard operable by the worker

DETAILED DESCRIPTION

A cross-sectional view of a typical conventional roof assembly is shownin FIG. 1 . The structural deck 1 which supports the rest of the roofassembly is covered with a vapor barrier 2. Placed immediately above andon top of the vapor barrier is the moisture detection system detectionconductors 3 in a zoned X and Y configuration shown best in FIG. 3 .Thermal insulation 4 is installed above the vapor barrier then aprotection board 5 is installed above the thermal insulation 4. Thewater impervious membrane 6 is then installed on top of the protectionboard to complete the assembly. The detection system is placed on top ofthe vapor barrier as this is where any moisture will tend to migrate.

Referring to FIG. 2 , an X and Y detection zone using moisture detectiontape with flat conductors is shown. The detection tape 7 is placed inthe roof assembly in a cross configuration where the tip conductors 8,11 and the ring conductors 9, 12 are spliced together at the tapeintersection 13 and connected to the sensing device 15. The length ofthe detection tape 7 defines the grid spacing for the detection system.The shorter the tape section the tighter the zoned grid pattern whichsubsequently increases the sensitivity and leak location resolution ofthe system.

FIG. 3 provides a simple schematic illustrating the zone configurationand wiring connection along with a block diagram shown in FIG. 4 of themeasurement system and Internet connection. The X and Y detection zones14, are placed directly on the vapor barrier. The tip and ring detectiontape conductors are connected together at the sensing device 15.

The sensor tape is of laminated construction with the preferredconfiguration having a substrate of high-dielectric strength and twoflat copper conductors 11, 13 and 8, 9 adhered to the dielectricsubstrate 20. The high-dielectric strength substrate provides mechanicalstrength and electrical insulation from the surface it is applied to.The substrate is coated with a pressure sensitive mounting adhesive thatprovides adequate adhesion to standard building materials such as wood,wood laminates, concrete, steel, galvanized steel, PVC, ceramic, etc.for attachment to the vapor barrier 2. The adhesive backing is desirablynon-water soluble and selected to provide good adhesion characteristicsover the anticipated application temperature range, e.g. −10° C. to +50°C. The adhesive backing is protected prior to installation by a peel-offrelease layer (not shown). A protective non-hygroscopic dielectric layerover the conductors provides mechanical and insulating properties suchthat contact with metal surfaces does not cause a short circuit acrossthe conductors while allowing water to penetrate to the conductorsurfaces and bridge the gap between the conductors.

The conductors are preferably flat metal strips typically no less than6.5 mm wide and spaced apart by a distance no less than 13 mm,preferably 13.6 mm.

FIG. 3 demonstrates a cross grid detection zone using moisture detectiontape with flat conductors is shown. The detection tape is placed in theroof assembly in in a cross configuration, see FIG. 3 for layout ofmultiple cross grid detection zones. It will be noted that the twosensing tapes 14A and 14B are arranged at right angles and intersect atthe middle of the zone.

The sensing device is also connected to a humidity sensor 15A and to atemperature sensor 15B. Thus the sensing device 15 in each zone can beused to detect the presence of moisture using the tapes 14A and 14B andalso the temperature and humidity. The sensors are interrogated asrequired by the sensor device so that the sensor device receives data asrequired for communication to the central control shown in FIG. 4 .

Referring to FIG. 4 a portion of a roof assembly is shown with a zonedarea 14C with remote monitoring sensor and signaling electronicsdefining the sensor device 15 installed on the vapor barrier or roofdeck. The moisture detection sensor 14A, 14B is placed along the widthand length of the zone with the RMSE 15 located in the center of thezone 14 and the sensors connected to an input of the RMSE 15. All thezones are daisy chain connected using a multi pair cable 16. The cableis terminated in a control panel 17 containing a CAN bus 18, tonegenerator 19, powering pair 20, microcontroller 21 and an internetgateway 22. The control panel 17 is connected through the gateway 22 toa cloud server 23. A monitoring site 24 is connected to the controlpanel 17 via the cloud sever through the internet. At the monitoringsite 24 sensor date is downloaded displayed and analyzed. When requiredthe monitoring site can issue commands to enable the locate tone at aselected zone for further identification.

Referring to FIG. 5 , a detailed arrangement of the remote measurementand signaling electronics is illustrated. A powering pair 25 of theconnecting cable supplied by power supply 20 terminates on the powersupply circuit 26 of the sensor device 15 which powers the unit. Asecond pair 27 of the cable system connects the CAN bus 18 to thetransceiver 28 of the unit 15. A microprocessor 29 with a unique codeidentity receives commands and transmits data through the CAN bustransceiver 28. On command from the microprocessor 29 using commandsignals from the CAN bus sensor measurement device 30 takes readingsfrom the sensors 14A, 14B, 15A and 15B and sends the information to themicroprocessor 29 for transmission.

In order to provide remote locating of the sensor unit 15 in therespective zone 14 to ensure that the sensor unit believed to besignalling a water penetration is actually at the location expected,when commanded on the CAN bus from the central unit, the microprocessor29 sends a signal to a coil switch 32 which acts to energize a locatecoil 33 from the tone signal transmitted on a third cable pair 34 of theconnecting cable.

The arrangement above thus provides a method of detecting a leak in aroof of FIG. 1 , wherein the roof comprises a generally horizontal roofsupport deck with a water impermeable membrane applied on top of theroof assembly

As shown above, the total area of the membrane 6 to be monitored isdivided into a plurality of separate zones 14 and in each zone a sensordevice 15 arranged to detect moisture is positioned underneath themembrane 6.

The sensor device 15 in each zone includes remote measurement andsignaling electronics shown in FIG. 5 . Each unit 15 is assigned aunique digital code address form communication on the CAN bus 18. TheCAN bus system allows the connection of all of the units 15 includingthe remote measurement and signaling electronics of the sensor devicesto a single power and signaling cable system generally indicated at 40defined by the pairs 25, 27 and 34 using a daisy chain arrangement. Thesignalling cable system 40 is terminated in the serial bus controllerwhich is used to interrogate each of the sensor devices on the daisychain connection using the address to identify zones where moisture isdetected.

The serial bus controller 21 includes built in loop verificationtesting. A The distal end of the signalling cable 40 the can bus cable29 is terminated in a 120 ohm resistor (not shown) which terminates thepair electrically for both impedance matching and cable continuitytesting.

The signalling cable system 40 contains a conductor pair 29 for theserial bus for communication with the sensor devices and a conductor apair 25 for powering the sensor devices.

In this way, the sensor devices are interrogated from the remotemonitoring station 17 reading moisture levels in a location surroundingthe sensor device 15 and mapping the levels onto a chart 24 foranalysis.

A further embodiment is shown in FIGS. 6 to 11 .

In this embodiment, a moisture detection sensor 57 is mounted underneatha membrane of a flat roof assembly shown at 56 and as described above inrelation to FIG. 1 . The sensor 57 includes a moisture detection systemusing the moisture responsive tapes 14A and 14B as described above andoptionally the humidity and temperature sending components 15A and 15Balso as described above. The sensor 57 also includes a control circuit55 which operates to receive the signals from the moisture, temperatureand humidity sensors as required or when interrogated for communicationto a remote location.

In this embodiment the signals from the control circuit 55 arecommunicated to the remote location by a wireless hand-held scanningsystem 52. The hand-held device 52 includes a handle 53 with scanningelectronics circuitry mounted in a top portion 50 and a transmitting andreceiving antenna 54 mounted at or adjacent the bottom so as to be closeto the top surface of the membrane. The device 52 is held and supportedby a technician 51 carrying the device. However wheeled units can alsobe used.

The moisture detection sensor 57 with a sensing and transceiver circuit55 is connected to the powering and transmitting antenna 58. Thescanning unit 52 transmits a powering signal 54A, typically at around125 KHz, and simultaneously controls and communicates signals to andfrom a sensor transceiver component of the sensor 57, typically ataround 915 MHz.

FIG. 7 illustrated the 125 KHz powering transmitter circuit of the handheld device 52 where a 125 KHz oscillator 59 drives the input to a classE power amplifier 60 which is coupled to a resonant antenna circuitthrough a coupling capacitor 61 with a capacitance of C. An outputantenna 62 comprises a loop antenna with an inductance of L so that theseries circuit LC is selected to resonate at the 125 KHz poweringfrequency. At resonance, the antenna 62 creates the maximum inductivefield 54A which couples to the powering antenna 58 of the sensor unit57.

FIG. 10 details the circuit which powers the sensor unit 57 includingthe microprocessor and transceiver 55. The powering antenna 58 consistsof the inductive loop 63 and the series capacitor 61 that is resonant at125 KHz and is energized by the scanner antenna 62 of the unit 57. Thepowering circuit 66 includes a full wave bridge rectifier 67 a storagecapacitor 68 and a Schmitt trigger 69. When the storage capacitor 68reaches five volts the Schmitt trigger 69 turns on a transistor 70energizing the entire circuit. Once energized the resistance measuringcircuit 71, shown in FIG. 9 , reads the resistance of the moisturedetection tapes 14A, 14B which is connected across the input 72 which isproportional to the moisture in the respective zone 14. The circuit 71provides an output 74 which is indicative of the moisture sensed by thetapes. This is converted to a digital signal by an A/D circuit 81.

The structure of the sensing unit 55 is shown in FIG. 8 . The structureof the hand-held unit 52 is shown in FIG. 11 .

The analog output 74 of the measuring circuit 72 is supplied to an A/Dinput 74 b of the microprocessor 18 b is sent to the transceiver 77 ofthe sensing unit 55. The transceiver 77 of the sensor unit 55communicates with the transceiver 78 of the hand-held unit 78.

Each of the transceivers 77 and 78 includes a transmission antenna 79,80 which is a pc-based antenna and acts to transmits the digital databetween the two transceivers.

The transceiver 78 and microprocessor control 81 of the hand-held unit52 as shown in FIG. 11 receive and manage the data transmitted includinginterrogating signals and data signals providing the required moisturepenetration data. The received data is presented on a display 82. Akeyboard 83 is used to store the data in memory and call up other testresults such as the temperature and humidity sensors 15A and 15B, wheninstalled on the sensor unit, in a serial bus configuration 74C.

This system therefore incorporates a hand-held scanning unit 52 whichgenerates a powering field in the antenna 54 which energizes the antenna58 of the sensor system 55 located in the roof or wall assembly. Onceenergized, the sensor and scan unit communicate using a UHF low powertransceiver system 77, 78 using antennas 79 and 80. On command,moisture, and optionally temperature and humidity readings, are takenand transmitted to the scanning unit 52 for display and storage.

The method of detecting a leak in a roof in this embodiment includes ineach zone installing during application the membrane at or adjacent themembrane the sensor device 55 arranged to detect moisture underneath themembrane.

The movable scanning device includes the power supply antenna 62 forsupplying power by an electromagnetic wave to the input power supplycircuit 66 shown in FIG. 10 of the sensor device 57 using the inputantenna 58.

When required, for example for periodic assessment or maintenance, thescanning device is transported by the technician to select one of thezones. Typically, the technician will scan all zones in a patterncorresponding to the array as laid out during installation. When thehand-held device passes over or moves adjacent to a respective one ofthe sensor devices, the power supply signal from the antenna of thehand-held device acts to power up the sensing device which is otherwiseunpowered and dormant. The sensing device then responds with a signalfrom the transceiver which is received by the transceiver of thehand-held device and provides an output audible or visible by thetechnician to indicate location of the zone and its associated sensingdevice.

Using the power supplied, the sensor device acts to emit signals relatedto the detection of the presence of or level of moisture underneath themembrane as detected by the measuring tapes of the sensor device. Thesignals are detected at the mobile scanning device and relayed to thetechnician on the display or to be recorded. In this way the status ofthe roof membrane can be monitored periodically as required to detectany water penetration and the extent of that penetration.

Thus each sensor device is unpowered and unconnected to power supplywires and the sensor devices provide a wireless moisture measuringsystem. This avoids the necessity to provide wiring arrangements whenthe roof is installed which can become damaged or may be improperlyinstalled thus losing contact with one or more of the sensors.

The antenna uses a low frequency resonant antenna system in the scanningunit and the sensor device to energize a sensor measurement circuit todetect the moisture underneath the membrane. If desirable, and in adifferent circuit arrangement, the low frequency energizing signal canbe modulated to communicate and transmit data between the scanning andsensor unit.

When energized, the sensor device communicates with the scanning unitvia UHF transceivers 77 and 78 employed in both the scanning unit andsensor device.

While the system can operate simply to monitor moisture penetration, insome cases each sensor device also includes a sensor 15A for humidity ina location surrounding the sensor device and/or a sensor 15B fortemperature in a location surrounding the sensor device.

1. A method of detecting a leak in a roof, wherein the roof comprises agenerally horizontal roof support deck with a water impermeable membraneapplied on top of the roof assembly, the method comprising: dividing themembrane into a plurality of separate zones; in each zone applying at oradjacent the membrane a sensor device arranged to detect moistureunderneath the membrane; the sensor device in each zone including remotemeasurement and signaling electronics; assigning a unique digital codeaddress to each of the remote measurement and signaling electronics;connecting inputs of the remote measurement and signaling electronics ofthe sensor devices to a single power and signaling cable system using adaisy chain; terminating the signalling cable system in a serial buscontroller; and using the serial bus controller to interrogate each ofthe sensor devices using the address to identify zones where moisture isdetected.
 2. The method according to claim 1 wherein each sensor devicealso includes a sensor for humidity in a location surrounding the sensordevice.
 3. The method according to claim 1 wherein each sensor devicealso includes a sensor for temperature in a location surrounding thesensor device.
 4. The method according to claim 1 wherein the serial buscontroller is driven by a microprocessor controller which is connectedto a remote server through an internet gateway.
 5. The method accordingto claim 1 wherein the serial bus cable has at least one pair with atermination resistor of a known value at the distal end for looptesting.
 6. The method according to claim 1 wherein the signalling cablesystem contains a conductor pair for the serial bus for communicationwith the sensor devices and a conductor a pair for powering the sensordevices.
 7. The method according to claim 1 wherein the sensor devicesare interrogated from a remote monitoring station reading moisturelevels in a location surrounding the sensor device and mapping thelevels onto a chart for analysis.
 8. The method according to claim 1wherein each sensor device includes an antenna for emitting a locationsignal and a switching device for activating the antenna.
 9. The methodaccording to claim 1 including providing a locate tone signal and, oncommand at the sensor device, the locate tone is switched on at thesensor device to energize the antenna of the sensor device.
 10. Themethod according to claim 1 wherein the signalling cable system includesa dedicated conductor pair for the locate tone signal.
 11. The methodaccording to claim 1 wherein, on detection of moisture by a sensordevice, the locate tone is switched on to the respective antenna of thesensor device and a technician locates from above the membrane thesensor device emitting the tone signal using a locate receiver.
 12. Themethod according to claim 1 wherein the moisture is sensed by eachsensor device by applying to the roof in a location underneath themembrane and on top of the deck at least one length of a moisturedetection sensor tape arranged to detect moisture in between the deckand the membrane.
 13. The method according to claim 12 wherein themoisture detection sensor tape comprises a substrate of a dielectricmaterial carrying first and second elongate, parallel, conductorssecured to one surface of the substrate and moisture is sensed by asensing system detecting changes in resistance between said first andsecond conductors of said at least one length so as to detect moisturepermeating into the respective zone in the location between the membraneand the roof deck.
 14. The method according to claim 13 wherein said atleast one length is arranged in a two-dimensional array.
 15. The methodaccording to claim 12 wherein the said at least one length of each zoneis electrically separated from said at least one length of each of theother zones.
 16. The method according to claim 12 wherein said at leastone length comprises at least first and second lengths arranged to liein different directions in the zone.
 17. The method according to claim16 wherein the zones are rectangular and each of the first and secondlengths spans across the zone passing substantially through a center ofthe zone, either diagonally or parallel to sides of the zone.
 18. Amethod of detecting a leak in a roof, wherein the roof comprises agenerally horizontal roof support deck with a water impermeable membraneapplied on top of the roof assembly, the method comprising: dividing themembrane into a plurality of separate zones; in each zone applying underthe membrane a sensor device; wherein the sensor device includes sensorsarranged to detect moisture underneath the membrane, humidity in alocation surrounding the sensor device and temperature in a locationsurrounding the sensor device. the sensor device in each zone includingremote measurement and signaling electronics.
 19. A method of detectinga leak in a roof, wherein the roof comprises a generally horizontal roofsupport deck with a water impermeable membrane applied on top of theroof assembly, the method comprising: dividing the membrane into aplurality of separate zones; in each zone applying at or adjacent themembrane a sensor device arranged to detect moisture underneath themembrane; the sensor device in each zone including remote measurementand signaling electronics; wherein each sensor device includes anantenna for emitting a location signal and a switching device foractivating the antenna. where a locate tone signal, on command at thesensor device, the is switched on at the sensor device to energize theantenna of the sensor device; and wherein, on detection of moisture by asensor device, the locate tone is switched on to the respective antennaof the sensor device and a technician locates from above the membranethe sensor device emitting the tone signal using a locate receiver. 20.A method of detecting a leak in a roof, wherein the roof comprises agenerally horizontal roof support deck with a water impermeable membraneapplied on top of the roof assembly, the method comprising: dividing themembrane into a plurality of separate zones; in each zone applying at oradjacent the membrane a sensor device arranged to detect moistureunderneath the membrane; the sensor device in each zone including remotemeasurement and signaling electronics; assigning a unique digital codeaddress to each of the remote measurement and signaling electronics;connecting inputs of the remote measurement and signaling electronics ofthe sensor devices to a single power and signaling cable system using adaisy chain; terminating the signalling cable system in a serial buscontroller; wherein the serial bus controller includes built in loopverification testing.